Monarch butterflies vs. Hurricane Patricia: As the storm headed up Mexico, the flock was set to cross its path

The approach of Hurricane Patricia drove many residents and tourists away from the storm, but one group of seasonal visitors was flying directly into its path: the continent’s flock of monarch butterflies, which migrates to Mexico each fall.

October marks the insects’ annual approach through the country, which would have sent them across the record-setting storm’s route last week.

But those butterflies shifted their flight east, away from the hurricane’s track, according to the Mexican national agency tasked with tracking them.

The butterflies “changed their route from west to east and have taken refuge in the ravines” of the country’s eastern mountain range, the Sierra Madre Oriental, the National Commission of Natural Protected Areas (CONANP) reported.

Hurricane Patricia quickly transformed from a Category 1 storm on Thursday morning to a Category 5 storm early Friday afternoon. Patricia dissipated just as quickly, transforming into a Category 2 storm by the time it moved inland Saturday morning. (Photo: The Associated Press)

The weather itself may be partly to thank for the changing itinerary.

“Monarchs have the weight of a paper clip,” said Gail Morris, a monarch conservationist in Arizona. “With a strong wind, it doesn’t take much to blow them into another area.”

Morris explained that, based on past experience, the iconic butterfly’s eastward shift ahead of Patricia was likely a response to the change in wind directions associated with the storm. She is the coordinator for the Chandler-based Southwest Monarch Study, which monitors the flyways throughout Arizona of western monarch populations.

“The winds moving into the area ahead of a low pressure system could be, depending on the monarchs’ location… it would shift them farther east,” she said.

Photo: National Commission of Natural Protected Areas, Mexico

Alejandro del Mazo Maza, commissioner for CONANP, said the detour from the storm would likely delay by several days the arrival of a large number of the monarch population to their winter breeding grounds in central Mexico. They’re expected in early November, according to the agency’s report.

Monarch butterflies complete a remarkable migratory cycle, leaving Mexico each spring for the U.S. and Canada. After multiple generations through the year, the descendants of those butterflies leave in the fall, to fly back to their ancestors’ forests in the states of Mexico and Michoacan, west of Mexico City.

But the health of the migrating butterflies as a species has been the subject of recent concern larger than any one storm. In recent years, estimates of the total population spending the winter in central Mexico have shown the colonies in steep decline. Experts have blamed that on a variety of factors including logging and development in Mexico and changing farming practices in the United States that have depleted milkweed, the butterflies’ main food source.

The CONANP said this year’s migration-tracking effort, which started at the beginning of October, revealed that the monarch populations are in “good health.”

Morris echoed the report, stating that she had not heard, through her network of contacts and conservation groups, of mass mortality reports in Mexico.

“To me, it’s all good news,” she said. “One year ago or two, the weather was restricting them from moving. They’re right where they should be, and they’re moving forward.”

Forward, in this case, out of the path of the storm. Which raises one more question about the butterflies: Did the wind blow them aside, or did they somehow know to run to safety?

Morris said the answer is still unclear – there’s not enough research on their migration to know one way or the other.

“My gut reaction,” she said of the butterflies approaching a giant storm, “is that they responded to that.”